Vocabulary development is an essential goal in any language teaching program, and considering the multidimensional nature of this construct, achieving this goal needs effective assessment of all dimensions of word knowledge, i.e. breadth, depth and accessibility of word knowledge. Most of the current vocabulary assessment tools measure the breadth dimension of vocabulary (Christ, 2011). However, there have been studies which have developed "Selective" or "Productive" word association tasks (WAT) to measure depth of word knowledge (Meara & Fitzpatrick, 2000; Read, 1998). This study used both selective and productive WAT tasks to measure depth of word knowledge in 82 elementary and 71 advanced EFL learners to explore which format is better for assessing deep word knowledge for each group. Results showed that elementary learners did better in selective format while advanced learners acted better in productive format.